This fixes two issues with --trace-wasm-decoder and --trace-liftoff.
First, cache state tracing in liftoff only makes sense together with
--trace-wasm-decoder, so disable it otherwise.
Second, we were sometimes hitting a DCHECK with --trace-wasm-decoder on
functions which bailed out to Turbofan, since the bailout was resetting
the end pointer of the decoder to the current pc.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: Ib4e052a1cdec6389b12b4a0ea57f07c031324ed5
Reviewed-on: https://chromium-review.googlesource.com/853493
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50415}